Anti-ESD Photomask with Non-Conductive Mo Layer
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Solution Overview
Problem
During the photolithography process in semiconductor device fabrication, electrostatic discharge (ESD) can occur due to the movement of electrons and electron holes, potentially damaging the circuit lines and patterns on the photomask, leading to defects in the produced semiconductor devices.
Innovation Solution
An anti-ESD photomask is developed with a non-conductive layer formed on its surface to reduce conductivity and mobility of electrons and holes, while maintaining high light transmittance and critical dimension, suitable for use with ArF excimer lasers. The photomask includes a substrate with a light-shielding layer and a non-conductive layer, where the non-conductive layer is formed using oxides, nitrides, and oxynitrides containing Si and Mo, with a thickness between 1 nm to 3 nm to minimize conductivity without compromising light transmittance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a light-shielding layer is formed on the photomask to define circuit patterns, then the circuit pattern definition capability is improved, but electrostatic discharge (ESD) damage risk increases due to conductivity of the metallic light-shielding layer
Solution Approach 1:
The patent applies a composite structure consisting of a light-shielding layer (Mo-containing layer) combined with a non-conductive layer. The light-shielding layer maintains circuit pattern definition capability while the non-conductive layer (formed by surface treatment converting metallic Mo atoms to oxides, nitrides, or oxynitrides) reduces ESD damage risk by lowering surface conductivity. This composite material approach resolves the contradiction between needing conductive metallic layers for pattern definition and avoiding ESD damage from their conductivity.
Solution Approach 2:
The patent changes the chemical state and conductivity parameter of the light-shielding layer surface by performing surface treatment that converts metallic Mo atoms into non-conductive oxides, nitrides, or oxynitrides. This parameter change reduces surface conductivity from conductive to non-conductive state, thereby reducing ESD damage risk while preserving the light-shielding functionality for circuit pattern definition.
2Object-affected harmful factors
If a non-conductive layer is formed on the photomask to reduce ESD risk, then ESD damage risk is reduced, but light transmittance may be compromised
Solution Approach 1:
The non-conductive layer is formed with specific local properties: it is disposed on the light-shielding layer and has controlled thickness (1 nm to 3 nm) and composition (oxides, nitrides, or oxynitrides of Mo and Si). This local quality control ensures sufficient ESD protection while maintaining adequate light transmittance for the photolithography process, resolving the contradiction between ESD protection and light transmission requirements.
3Object-affected harmful factors
If the non-conductive layer thickness is increased to reduce conductivity, then ESD protection is improved, but light transmittance decreases
Solution Approach 1:
The patent optimizes the thickness parameter of the non-conductive layer to a specific range (1 nm to 3 nm). This parameter optimization achieves the right balance: sufficient thickness to reduce surface conductivity and provide ESD protection, while thin enough to maintain adequate light transmittance for effective photolithography exposure. This resolves the contradiction between ESD protection and light transmittance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The anti-ESD photomask effectively reduces the risk of electrostatic discharge damage, maintaining high light transmittance and preserving the critical dimension of the photomask, thereby reducing defects in semiconductor devices when used with ArF excimer lasers.
Implementation Method 1
electrostatic discharge (ESD) is likely to occur during the exposure process, and results in discharge of small current between two isolated portions of a conductive pattern
Implementation Method 2
The small current may result from movement of electrons and electron holes coming from a photoelectric effect during the exposure process
Implementation Method 3
the portion not covered by the light-shielding layer of the anti-ESD photomask of the present disclosure has a high light transmittance
Data Source
AI summary
The present disclosure provides an anti-ESD photomask and method of the same. In the method, a substrate is provided first. Then, a light-shielding layer is formed on a portion of the substrate, in which the light-shielding layer includes a Mo-containing layer. Next, a surface treatment operation is performed to convert a surface of the portion of the substrate and a surface of the light-shielding layer into a non-conductive layer.